Platelet MAO activity has been reported to be lower in some schizophrenic patients, perhaps chronic patients with hallucinations. We will continue our study of this using the Present State Examination to obtain detailed phenomenological and diagnostic data. Platelet MAO studies with other diagnoses, determinations of drug effects (lithium, TRH, antidepressants), relationship to clinical change, and relevant animal studies will also be carried out. A study of normal university student MAO activity and psychopathology will be carried out in collaboration with Prof. Bertram Cohler. Decreased serum DBH activity has been found by us in three studies of psychotic depressed patients. We will replicate this, study fluctations in serum DBH, characterize serum DBH inhibitors in those patients with fluctuating serum DBH. The effect of clozapine and amphetamine on serum DBH will also be studied. Erthrocyte ATPase may be decreased in depressed patients and increased in schizophrenics. We will verify this and study the relationship between Na ion - K ion- ATPase activity and the lithium erythrocyte/plasma ratio. The studies should clarify the diagnostic and prognostic usefulness of these three peripheral biochemical processes.